Hoist line sling for lifting heavy loads

ABSTRACT

A hoist line sling for lifting heavy loads, consisting of an elongated web (either fabric or metal mesh) has a triangularly shaped metal eye attached to each end thereof in a manner which assures that the stresses which exist in the web as tension loads are applied to the sling through the eyes at the ends thereof, are at all times concentrated in the transversely medial portion of the web containing its longitudinal neutral axis.

' United States Patent w13,ss3,7s0

Roy Norton c/o The Wear-Flex Corp., 4111 N. Washington Ave., Milwaukee,Wis. 53212 [21} Appl. No. 743,388

[221 Filed July 9, 1968 [45] Patented June 8,1971

[72] inventor [54] HOIST LINE SLING FOR LIFTING HEAVY LOADS 17 Claims,17 Drawing Figs.

[52] 0.8. CI 294/74, 24/200 [51] int. Cl. B66e1/18 [50] Field of Search24/ 197,

200, 265 BC, 265 81-1, 201.1, 265 CID; 74/230.5, 229, 241; 294/74-77[56] References Cited UNITED STATES PATENTS 3,343,862 9/1967 Holmes294/74 873,044 12/1907 Hanson 294/74 1,341,033 5/1920 Bear 24/197X1,490,066 4/1924 Carr 294/74X 2,056,844 10/1936 Farrand 74/229 2,266,18112/ l 941 Epps 294/74UX 2,843,905 7/1958 Brubaker 24/200 2,901,8019/1959 Girodet 24/200 2,970,358 2/1961 Eisner 24/265X 3,075,268 III 963Schwartz. 24/200 3,21 1,489 10/ l 965 Gill 294/ 74X FOREIGN PATENTS809,351 7/1951 Germany 294/74 210,668 1/1967 Sweden 294/74 OTHERREFERENCES One page from the Wear-Flex Corporation 5 catalog of nylonslings, ill/66 Primary ExaminerEvon C. Blunk Assistant Examiner-W. ScottCarson Attorney-Ira Milton Jones ABSTRACT: A hoist line sling forlifting heavy loads, consisting of an elongated web (either fabric ormetal mesh) has a triangularly shaped metal eye attached to each endthereof in a manner which assures that the stresses which exist in theweb as tension loads are applied to the sling through the eyes at theends thereof, are at all times concentrated in the transversely medialportion of the web containing its longitudinal neutral axis.

PATENTEU JUN 8 I97! SHEET 1 [1F 5 Flay Narzan m PATENTED JUN men 3583750SHEET 2 UF 5 PATENIEU JUN 8 1971 SHEET ll UF 5 II/"III" mm; 22 2 m2PATENTEB JUN 81911 3; 583; 750

sum 5 [1F 5 12a Narzarz I'IOIST LINE SLING FOR LIF'IING HEAVY LOADS Theinvention resides in the discovery that the side edge portions of awebsuch as the flexible web of a hoist line lifting sling-will not estressed to the point of causing premature failure of the web if thestress in the web resulting from heavy tension loads thereon is alwaysconcentrated in a zone which contains, or is as close as possible to,the longitudinal neutral axis of the web. This objective is achieved byproviding the rigid members to which the web is attached, and throughwhich tension is applied to the web (and/or such other rigid memberswith which the web may have load bearing engagement) with convexlycurved surfaces that extend transversely across the web and provide theload transmitting connections between the web and the rigid members.

Experience has shown that load lifting slings of the type to which thisinvention pertains, and which are customarily known as hoist lineslings, made in accordance with conventional practice and design, alwaysfailed or broke first at the side edges of the web, and as soon as abreak occurred at one of the side edges, the tear would quickly runacross the full width of the web. Heretofore, the only known way ofcombatting such failures of the web was to use what is known ascalibrated webbing, or webbing having a higher overall tensile strengthrating. Calibrated webbing has increased thickness at the edges withcorrespondingly higher tensile strength than the transversely medialportion of the webbing along its longitudinal neutral axis. Both ofthese expedients increase the cost of the sling and reduce itsflexibility. Moreover, while slings made with calibrated or highertensile strength webbing could handle heavier loads without failure,when failure did occur it still always started at one or the other ofthe side edges of the web.

The answer to the problem, as indicated in the aforesaid Summary,resided in the discovery that by providing the connection between eachend of the web and its respective eye with some means which at all timestends to concentrate the stress to which the web is subjected by tensionloads thereon, in a transversely medial portion of the web whichcontains or is as close as possible to the longitudinal neutral axis ofthe web, the stresses in the side edge portions of the web areproportionately reduced, and do not reach the disruptive magnitude whichgave rise to the problem. Tests have demonstrated that when slingembodying this invention are deliberately subjected to breakage, theinitial failure no longer is limited to the side edges of the web as itwas in the past. Tests have also shown that without any increase intensile strength rating of the webbing or any other modificationthereof, the slings embodying this invention can handle heavier loadswithout failure.

Broadly stated, therefore, the purpose and object of the invention is toprovide some means (wherever a websuch as that of a load liftingsling-is attached to a rigid connector element or passes over or arounda rigid supporting element) by which the stresses in the web incident toits being placed in tension are at all times concentrated in atransversely medial zone or portion of the web which contains, or is asclose as possible to, the neutral axis of the web.

More specifically, the purpose and object of this invention is toprovide an improved industrial load lifting sling of the type consistingof a flexible web with a metal loop or eye at each end thereof. Moreparticularly, it is the purpose and object of the invention to soconstruct and design the connection between the ends of the web and themetal eyes that, during use of the sling, no significant difference everexists in the level of the stresses in the side edge portions of the webfrom that of the stresses which obtain in the transversely medialportion of the web along its neutral axis. Hence, without resorting tothe use of specifically calibrated or higher tensile strength ratedwebs, the slings can carry heavier loads without failure.

With these observations and objects in mind, the manner in which theinvention achieves its purpose will be appreciated from the followingdescription and the accompanying drawings. This disclosure is intendedmerely to exemplify the invention. The invention is not limited to theparticular structure disclosed and changes can be made therein which liewithin the scope of the appended claims without departing from theinvention.

The drawings illustrate several complete examples of the physicalembodiments of the invention constructed according to the best modes sofar devised for the practical application of the principles thereof, andin which:

FIG. 1 is a plan view of the opposite end portions of a sling of thetype to which this invention pertains, showing the same in its relaxedcondition;

FIG. 2 illustrates one manner of using the sling, which is generallyreferred to in the trade as a basket hitch";

FIG. 3 illustrates another way of lifting a load with the sling of thisinvention, known as a choker hitch";

FIG. 4 is a cross-sectional view through FIG. I on the plane of the line4-4;

FIG. 5 is a plan view, similar to FIG. 1, but showing only one end ofthe sling and under load, part of the loop at the end of the web beingbroken away and in section;

FIGS. 6 and 7 are views similar to FIG. 5, but illustrating two modifiedembodiments of the invention;

FIG. 8 is a cross-sectional view through FIG. 7 on the plane of the line8-8;

FIG. 9 is another view similar to FIG. 5, illustrating still anothermodified embodiment of the invention;

FIG. 10 is a cross-sectional view through FIG. 9 on the plane of theline 10-10;

FIG. 11 is a view similar to FIG. 5, illustrating what might beconsidered a reversal in the arrangement of the parts forming theconnection between the web and the eyes at the ends thereof, from thatemployed in the other embodiments of the invention.

FIG. 12 is a cross-sectional view through FIG. 11 on the plane of theline 12-12;

FIGS. I3 and 14 are diagrammatic views to better illustrate how the loadconcentrating means incorporated in the connection between the ends ofthe web and the eyes distributes the stresses across the width of theweb, and keeps the side edge portions of the web from being overstressed;

FIG. I5 is a perspective view of the spool of a ratchet-type webtensioner embodying this invention;

FIG. I6 is a perspective view illustrating a sling equipped with cornerguards to protect the web of the sling against being cut by sharp edgeson the load being lifted, and which comer guards embody this invention;and

FIG. 17 is a perspective view of one of the corner guards of the slingshown in FIG. 16, at an enlarged scale to better illustrate theadaptation of this invention thereto.

Referring now more particularly to the accompanying drawings in whichlike numerals indicate like parts, and especially to FIGS. 1 to 5,inclusive, the numeral 5 denotes the fabric web of a load lifting slingespecially adapted for industrial use. The ends of the web haveattaching eyes 6 and 7 connected thereto. Each eye has a rigid crossbar8 to which the web is connected and the eye 6 has a second crossbar I0joining its side legs 9 at a distance from and parallel to the crossbar8. The space between the crossbars 8 and I0 and the portions of the sidelegs spanning the same is large enough to have the eye 7 at the otherend of the web passed therethrough to enable the sling to be used as achoker hitch, (shown in FIG. 3) as well as a vertical hitch (shown inFIG. 2). Each end of the web has a loop I2 formed thereon, in which therigid crossbar 8 of its respective eye is received. The loops I2 areproduced in the conventional manner by passing the end portion of theweb around the crossbar and then sewing, or otherwise bonding, the samesolidly to the underlying portion of the web.

Heretofore, the crossbars of the eyes embraced by the loops I2-or atleast the transversely curved surfaces thereof that are engaged by theloops when the sling is under load-were longitudinally straight from endto end. Theoretically, with that straight line relationship, thestresses in the web as a load was lifted should have been substantiallyuniform across the full width of the web, but they were not at alluniform. That ideal condition could only exist if the lines of forceduring use of the sling always remained exactly normal to the straightline engagement between the web loops and the crossbars of the eyes.

In practice, however, the angle between the lines of force and thestraight line engagement of the web loops with the crossbars of theeyes, was different from job to job, and even during lifting of a loadit was apt to change. As a result, the side edge portions of the webwere constantly and alternately subjected to higher stresses than thetransversely medial portion of the web. This caused the side edgeportions of the web to be strained to the point of breakage and resultedin failure of the web at loads considerably less (up to percent less)than would have been the case if the stresses were uniformly distributedacross the width of the web.

The consequences of alternately concentrating the lifting stresses inthe side edge portions of the web are graphically illustrated by thecondition of an old fashioned pair of suspenders that has been subjectedto prolonged and perhaps severe usedboth side edges are ruffled andanything but straight as they were when the suspenders were new. In thecase of the suspenders, the consequences of overstressing the side edgeportions seldom did more than detract from the sartorial appearance ofthe wearer, but in the load lifting slings heretofore available itresulted in premature failure of the sling.

By virtue of this invention, a relatively slight structural change inthe connection between the ends of the web and the adjacent eyesrelieves the side edge portions of the web of the disruptive stresses towhich they would be subjected without the benefit of this invention. Inthe embodiment of the invention illustrated in FIGS. l5, inclusive, thischange consists in so shaping the rigid crossbars 8 that the surfacesthereof engaged by the loops 12 when the sling is under load are crownedor convexly curved from end to end, as indicated at 13 in FIG. 5. Incross section, the crossbars 8 may be round or ovalshaped, as shown, inwhich event the major axis lies in the medial plane of the eye.

By virtue of the endwise extending convex curvature of the crossbars 8,when the sling is relaxedas shown in FIG. 1- -the side edge portions ofits loops 12 are spaced from the crossbar, as indicated at 14 in FIG. 1.Accordingly, when a load is applied to the sling-and assuming that theresulting lines of force are normal to the axis of the crossbar 8 andhence normal to a line extending transversely across the web at rightangles to its side edges-as in FIG. 13-that load is initially appliedupon the transversely medial portion of the web along its neutral axis,since the crossbars 8 are rigid and retain their shape even when thesling is lifting a heavy load. Only after the medial portion of the webhas been stressed, are stresses manifested in the side edge portions ofthe web. The arrows in FIG. 13 depict both the direction of the lines offorce and the relative magnitude of the stresses across the width of theweb. In this case-which is by no means the usual situation during use ofthe sling-the stresses in the web are concentrated in the transverselymedial portion of the web along its neutral axis and are progressivelyless in the portions of the web at opposite sides of the neutral axis.

FIG. 14 illustrates how during use of the sling, the angle between thelines of force and the axis of the cross bar 8 deviates from the idealcondition, and how this invention precludes overloading stresses in theside edge portions of the web and consequent premature failure of theweb and, on the contrary, reduces the differential between the stressesin the loaded side edge portion and in the medial portion of the web.Since the direction in which the crossbar 8 inclines will alternateduring use of the sling between that shown in FIG. 14 and the oppositethereof, it follows that this reduction in differential obtains at bothsides of the neutral axis, with the result that the stresses in the webare more uniformly distributed across the width thereof.

When the sling is used as a choker hitch, as shown in FIG. 3, a medialportion of the web engages the second crossbar 10 which, like thecrossbars 8, is rigid and has the surface 15 thereof-which is engaged bythe web-longitudinally convex, as clearly shown in FIG. I. As a resultof the convex curvature of the surface 15, the side edge portions of theweb bearing thereagainst are not as stressed as they would be in theabsence of such convex curvature.

Preferably the divergent end portions 16 of the side legs 9 are largerin cross section than the adjacent end portions of the crossbars 8,which results in the provision of shoulders 17 to hold the loops of theweb properly positioned on the crossbars 8 and, as best seen in FIG. 4,the shoulders 17 also provide ribs or runners to protect the loops fromcontact with surfaces that would otherwise cause abrasion, as when oneend of the sling is slipped across the floor under a load preparatory tolifting the same.

It is also preferable to have the thickness of the eye convergentlytapered from its crossbar 8 to its crane hook engaging apex 9'.

The invention is, of course, not limited to adaptation in the mannerillustrated in FIGS. I-5, inclusive, wherein the eyes are permanentlyattached to the ends of the fabric web. Thus, for instance, each eye canbe replaced by a clevice 20 with a removable crosspin 21, as shown inFIG. 6. In this case, a crowned spool 22 mounted on the crosspin betweenthe legs of the clevis provides the convexly curved surface 23 by whichthe application of overloading stresses upon the side edge portions areprevented.

FIGS. 7 and 8 illustrate an embodiment of the invention which-like thatof FIG. 6-employs a clevis 20 and a remova ble crosspin 21but in thiscase the spool is supplanted by a saddle 25. The top of the saddle 26 isround in cross section, as shown in FIG. 8, and also crowned or endwiseconvex as seen in FIG. 7. Flanges 27 hold the loop of the fabric web inposition and protect the same against abrasion; and to hold the saddleassembled with the crosspin 21, a small pin 28 having a drive fit in acrossbore through the pin 21, has its end portions loosely received inholes 29 in the sides of the saddle. By virtue of the size of the holes29 in comparison to that of the end portions of the pin 28, and the factthat the space between the side portions of the saddle is larger thanthe transverse width of the pin 21, it follows that the saddle is freeto rock from side to side during use of the sling. This allows the slingto accommodate itself to the load without sliding on the saddle.

The embodiment of the invention illustrated in FIGS. 7 and 8 has anadditional feature not possessed by the slings of FIGS. 1-6, inclusive.This feature, which may be regarded as edgewise accommodation of the webin its connection to the eye or clevis, is obtained by having theundersurface 30 of the saddle convexly curved from end to end, as shownin FIG. 7. As will be apparent, it is therefore possible for the saddleto rock lengthwise thereof on its supporting pin 21 and therebyaccommodate any tendency of the load to shift the web edgewise in onedirection or the other.

The embodiment of the invention illustrated in FIGS. 9 and 10 possessesall of the features found in the saddle version of the connection shownin FIGS. 7 and 8, with the exception of the ready removability of thepin 21 In this case, the crosspin 21 has cylindrical end portions thatare received in appropriate holes in the legs of the clevis 20 and heldagainst disassembly therefrom by pins 33 driven into the end portions ofthe crosspin 21' and loosely received in holes in the hubs of theclevis.

The primary distinction between the embodiment of the invention shown inFIGS. 9 and 10 and that of FIGS. 7 and 8, however, resides in the factthat instead of a saddle loosely seated on the crosspin, a T-bar 34 hasits stem portion 35 received in a slot 36 in the crosspin 21 with thehead 37 of the T-bar resting on the crosspin. A pin 38 fixed in the stemportion of the T-bar with its ends projecting therefrom and looselyreceived in holes 38 in the crosspin, holds the parts assembled without,however, interfering with longitudinal rocking of the T-bar on thecrosspin 21. Such longitudinal rocking is possible by virtue of the factthat the underside of the head 37 is convexly curved from end to end;and to gain the desired concentration of load, the upper surface 39 ofthe head is convexly curved from end to end.

In the embodiments of the invention thus far described, the means forconcentrating the load upon the transversely medial portion of the webalong its neutral axis has been on that part of the connection (betweenthe web and eye) which is on the eye. The reverse relationship can beemployed, however, as illustrated in FIGS. 11 and 12. In this case, thecrossbar 8' of the eye is axially straight-at least as to the surfacethereof which is engaged by the loop of the web, and the underside ofthe loop has a pad 50 formed thereon, the underside of which is convexlycurvated transversely of the web and lengthwise of the crossbar 8.Accordingly, when the sling is relaxed, contact between the underside ofthe loop of the web and the crossbar 8 is confined to a small areasubstantially equispaced from the opposite edges of the web, to therebyconcentrate the load on the transversely medial portion of the web alongits neutral axis during use of the sling.

The pad 50 may be made of any suitable material having the requiredflexibility and compressive strength, and-as shown in FIG. 12-the pad 50preferably extends a substantial distance along the opposite stretchesof the loop.

The invention is also advantageously applicable to ratchettype webbingtensioners in which one end of a length of webbing is attached to theframe structure of a ratchet mechanism and the other end portion of thewebbing is wound up on a spool that is rotated and held by the ratchetmechanism. FIG. illustrates the spool 52 of such a ratchet device, whichin accordance with this invention has a convex curvature from end to endbetween the flanges 53 of the spool. Hence, as a webbing is wound uponthe spool and tensioned, the resulting stresses are concentrated in thetransversely medial portion of the webbing along its neutral axis.

Still another area in which this invention can be advantageously appliedis in connection with corner guards used with lifting slings to protectthe same against being cut by sharp edges on the load to be lifted. FIG.16 illustrates how such corner guards are used. Generally the cornerguard is a metal stamping or casting of right angular cross section toembrace a sharp edge of a piece to be lifted, and for convenience itusually has some means of keeping the guard assembled with the web ofthe sling.

As shown in FIG. 17, adaptation of the invention to the comer guardinvolved forcing the bend or junction 54 which connects the two flanges55 of the guard with a convexly curved outer surface. The curvature ismost pronounced on the plane which bisects the angle between the flanges55 and then merges gently into the planes of the flanges.

lnwardly directed fingers 56 at the opposite ends of the guard overliethe side edge portions of the web to hold the guard assembled with thesling, and preferably these fingers have their undersides convexlycurved to avoid sharp edged contact with the web.

From the foregoing description taken in connection with the accompanyingdrawings, it will be apparent to those skilled in this art that thepresent invention materially reduces the hazard of premature failure offlexible webs such as those of industrial load lifting slings, which inuse are subjected to tension loads along lines of force that are not atall times exactly normal to a line extending transversely across the webat right angles to its side edges, and in so doing significantlyimproves web-type load lifting slings.

What I claim as my invention is:

1. In a hoist line sling designed to lift and handle heavy industrialloads, and which sling comprises an elongated flexible web ofsubstantially uniform width and thickness throughout its length, andattaching members connected with the web and by which the web may beoperatively connected with a load and with a lifting hook, theimprovement by which the side edge portions of the web carry no morethan does the medial portion thereof of the stresses in the web thatresult from tension loads on the web during use of the sling, and whichimprovement resides in the connection between the web and each of saidattaching members, said connection comprising:

A. a rigid crossbar having an axis and being of a length slightlygreater than the width of the web, said crossbar extending transverselyof the web and having both ends thereof equally supportingly connectedwith the attaching member;

B. parts on said crossbar and on said web in load bearing engagement;

C. load concentrating means on one of said parts by which said stressesin the web during use of the sling are concentrated in the medialportion of the web as distinguished from its side portions, said loadconcentrating means comprising an elongated load bearing surface on saidone part extending transversely across the full width of the web andbeing con vexly curved along the length thereof, said convex curvaturebeing substantially symmetrical to the axis of said crossbar; and

D. said one part and the crossbar being sufflciently rigid to precludedeformation thereof by loads encountered during use of the sling.

2. In a hoist line sling, the structure of claim 1, wherein at least oneof the attaching members is an eye at one end of the web, and whereinsaid rigid crossbar is an integral part of said eye, and said part thatis on the web and has load bearing engagement with the crossbar is aloop formed in the web.

3. ln a hoist line sling, the structure of claim 1, wherein said onepart of the connection which has the convexly curved surface is on theweb.

4. In a hoist line sling, the structure of claim 3, wherein the part ofthe connection which is on the web is a loop formed by a portion of theweb and embracing the rigid crossbar, and wherein said one part whichhas the convexly curved surface is a pad on the inner surface of saidloop and in load bearing engagement with the rigid crossbar.

5. ln a hoist line sling, the structure of claim 1, wherein said onepart of the connection which has the convexly curved surface is on therigid crossbar.

6. The hoist line sling of claim 5, wherein said eye has divergent sidemembers joined to the ends of the crossbar with the side members andcrossbar lying in a common plane,

and wherein the portions of said side members that are contiguous to theends of the crossbar project transversely to said common plane beyondthe surfaces of the crossbar to provide shoulders at the ends of thecrossbar which hold the loop of the web properly positioned on thecrossbar and provide ribs to protect the web from contact with possiblyabrasive surfaces.

7. In a hoist line sling, the structure of claim 5, wherein said onepart of the connection which has the convexly curved surface is a memberseparate from but embracing the rigid crossbar.

8. ln a hoist line sling, the structure of claim 7, wherein the rigidcrossbar is round in cross section, and wherein said member which hasthe convexly curved surface is a flanged and crowned spool freelyrotatably mounted on the crossbar.

9. In a hoist line sling, the structure of claim 7, wherein said memberwhich has the convexly curved surface is a saddle of substantiallyU-shaped cross section, straddling the rigid crossbar, the top surfaceof the saddle being longitudinally crowned to provide the convexlycurved surface.

10. In a hoist line sling, the structure of claim 9, furthercharacterized by pins projecting from the sides of the crossbar andloosely received in holes in the adjacent portions of the saddle to keepthe saddle on the crossbar without restraining limited movement of thesaddle with respect to the crossbar.

1]. ln a hoist line sling, the structure of claim 10, wherein theunderside of the saddle is longitudinally convexly curved so that thesaddle can rock on the crossbar.

12. In a hoist line sling, the structure of claim ll, wherein thecrossbar is narrower than the space between the sides of the saddle, sothat the saddle has some freedom to rock from side to side as well aslongitudinally of the crossbar.

13. In a hoist line sling designed to lift heavy industrial loads, andwhich sling comprises an elongated flexible web of substantially uniformwidth and thickness throughout its length, and a rigid metal eyeconnected to each end of the web and by which the web may be operativelyconnected with a load and a lifting hook, the eye having spaced sidearms, the improvement by which the side edge portions of the web carryno more than does the medial portion thereof of the stresses in the webthat result from tension loads on the web during use of the sling, andwhich improvement resides in the connections between the web and theeyes, each of said connections comprising:

A. a rigid crossbar which forms an integral part of the eye and has bothends thereof equally supportingly connected to the spaced arms of theeye, said crossbar having an axis; B. a loop on the web embracing thecrossbar and having load bearing engagement therewith; C. loadconcentrating means by which said stresses in the web during use of thesling are concentrated in the medial portion of the web as distinguishedfrom its side edge portions, said load concentrating means comprising anelongated load bearing surface on the rigid crossbar extendingtransversely across the full width of the web and with which the loop onthe web has said load bearing engagement,

said load bearing surface being convexly curved along the length thereofwith the curvature substantially symmetrical to the axis of thecrossbar; and

D. said crossbar being sufficiently rigid to preclude deformationthereof by loads encountered during use of the sling,

114. ln a hoist line sling, the structure of claim 13, wherein saidcrossbar has a flat-sided slot therethrough, the flat sides of which areparallel to the general plane of the eye, and wherein said elongatedload bearing surface is the top of the head of a T-shaped member havingits stem received in said slot with the underside of the head of the Tbearing upon the crossbar at opposite sides of the slot.

15. In a hoist line sling, the structure of claim 14, wherein theunderside of the head of the T-shaped member is convexly curvedlongitudinally thereof so that the T-shaped member may rock lengthwiseof the crossbar.

16. in a hoist line sling, the structure of claim 14, wherein the topsurface of the head of the T-shaped member is transversely rounded.

17. A hoist line sling for lifting heavy industrial loads, whichcomprises a flexible web having parallel side edges, connected at eachend to a rigid eye, characterized in that:

A. each eye is substantially triangular in shape, with three connectedlegs, one of which forms a crossbar extending between the free ends ofthe other two legs;

8. loops on the ends of the web embracing the crossbars of the eyes tohave force transmitting engagement with the inner surfaces of thecrossbars during use of the sling, said crossbars being rigid andundeformable by loads lifted with the sling, and the inner surfaces ofthe crossbars being convexly curved lengthwise thereof so that duringuse of the sling and application of tension upon the web through an eye,the portion of the web medially of its side edges is stressed before anyload is placed upon the side edge portions of the web;

C. a second rigid crossbar connected to and bridging said other two legsof one of the eyes in parallel spaced relation to its first mentionedcrossbar, the space between the first and second crossbars and the legsto which they are connected being large enough to permit the e e at theother end of the web to be passed therethroug to enable the sling to beformed into a loop around a load to be lifted by a pull on the eye atsaid other end of the web,

and the surface of the second crossbar which faces the first crossbarbeing convexly curved lengthwise thereof and transversely rounded.

1. In a hoist line sling designed to lift and handle heavy industrialloads, and which sling comprises an elongated flexible web ofsubstantially uniform width and thickness throughout its length, andattaching members connected with the web and by which the web may beoperatively connected with a load and with a lifting hook, theimprovement by which the side edge portions of the web carry no morethan does the medial portion thereof of the stresses in the web thatresult from tension loads on the web during use of the sling, and whichimprovement resides in the connection between the web and each of saidattaching members, said connection comprising: A. a rigid crossbarhaving an axis and being of a length slightly greater than the width ofthe web, said crossbar extending transversely of the web and having bothends thereof equally supportingly connected with the attaching member;B. parts on said crossbar and on said web in load bearing engagement; C.load concentrating means on one of said parts by which said stresses inthe web during use of the sling are concentrated in the medial portionof the web as distinguished from its side portions, said loadconcentrating means comprising an elongated load bearing surface on saidone part extending transversely across the full width of the web andbeing convexly curved along the length thereof, said convex curvaturebeing substantially symmetrical to the axis of said crossbar; and D.said one part and the crossbar being sufficiently rigid to precludedeformation thereof by loads encountered during use of the sling.
 2. Ina hoist line sling, the structure of claim 1, wherein at lEast one ofthe attaching members is an eye at one end of the web, and wherein saidrigid crossbar is an integral part of said eye, and said part that is onthe web and has load bearing engagement with the crossbar is a loopformed in the web.
 3. In a hoist line sling, the structure of claim 1,wherein said one part of the connection which has the convexly curvedsurface is on the web.
 4. In a hoist line sling, the structure of claim3, wherein the part of the connection which is on the web is a loopformed by a portion of the web and embracing the rigid crossbar, andwherein said one part which has the convexly curved surface is a pad onthe inner surface of said loop and in load bearing engagement with therigid crossbar.
 5. In a hoist line sling, the structure of claim 1,wherein said one part of the connection which has the convexly curvedsurface is on the rigid crossbar.
 6. The hoist line sling of claim 5,wherein said eye has divergent side members joined to the ends of thecrossbar with the side members and crossbar lying in a common plane, andwherein the portions of said side members that are contiguous to theends of the crossbar project transversely to said common plane beyondthe surfaces of the crossbar to provide shoulders at the ends of thecrossbar which hold the loop of the web properly positioned on thecrossbar and provide ribs to protect the web from contact with possiblyabrasive surfaces.
 7. In a hoist line sling, the structure of claim 5,wherein said one part of the connection which has the convexly curvedsurface is a member separate from but embracing the rigid crossbar. 8.In a hoist line sling, the structure of claim 7, wherein the rigidcrossbar is round in cross section, and wherein said member which hasthe convexly curved surface is a flanged and crowned spool freelyrotatably mounted on the crossbar.
 9. In a hoist line sling, thestructure of claim 7, wherein said member which has the convexly curvedsurface is a saddle of substantially U-shaped cross section, straddlingthe rigid crossbar, the top surface of the saddle being longitudinallycrowned to provide the convexly curved surface.
 10. In a hoist linesling, the structure of claim 9, further characterized by pinsprojecting from the sides of the crossbar and loosely received in holesin the adjacent portions of the saddle to keep the saddle on thecrossbar without restraining limited movement of the saddle with respectto the crossbar.
 11. In a hoist line sling, the structure of claim 10,wherein the underside of the saddle is longitudinally convexly curved sothat the saddle can rock on the crossbar.
 12. In a hoist line sling, thestructure of claim 11, wherein the crossbar is narrower than the spacebetween the sides of the saddle, so that the saddle has some freedom torock from side to side as well as longitudinally of the crossbar.
 13. Ina hoist line sling designed to lift heavy industrial loads, and whichsling comprises an elongated flexible web of substantially uniform widthand thickness throughout its length, and a rigid metal eye connected toeach end of the web and by which the web may be operatively connectedwith a load and a lifting hook, the eye having spaced side arms, theimprovement by which the side edge portions of the web carry no morethan does the medial portion thereof of the stresses in the web thatresult from tension loads on the web during use of the sling, and whichimprovement resides in the connections between the web and the eyes,each of said connections comprising: A. a rigid crossbar which forms anintegral part of the eye and has both ends thereof equally supportinglyconnected to the spaced arms of the eye, said crossbar having an axis;B. a loop on the web embracing the crossbar and having load bearingengagement therewith; C. load concentrating means by which said stressesin the web during use of the sling are concentrated in the medialportion of the web as distinguisheD from its side edge portions, saidload concentrating means comprising an elongated load bearing surface onthe rigid crossbar extending transversely across the full width of theweb and with which the loop on the web has said load bearing engagement,said load bearing surface being convexly curved along the length thereofwith the curvature substantially symmetrical to the axis of thecrossbar; and D. said crossbar being sufficiently rigid to precludedeformation thereof by loads encountered during use of the sling.
 14. Ina hoist line sling, the structure of claim 13, wherein said crossbar hasa flat-sided slot therethrough, the flat sides of which are parallel tothe general plane of the eye, and wherein said elongated load bearingsurface is the top of the head of a T-shaped member having its stemreceived in said slot with the underside of the head of the T bearingupon the crossbar at opposite sides of the slot.
 15. In a hoist linesling, the structure of claim 14, wherein the underside of the head ofthe T-shaped member is convexly curved longitudinally thereof so thatthe T-shaped member may rock lengthwise of the crossbar.
 16. In a hoistline sling, the structure of claim 14, wherein the top surface of thehead of the T-shaped member is transversely rounded.
 17. A hoist linesling for lifting heavy industrial loads, which comprises a flexible webhaving parallel side edges, connected at each end to a rigid eye,characterized in that: A. each eye is substantially triangular in shape,with three connected legs, one of which forms a crossbar extendingbetween the free ends of the other two legs; B. loops on the ends of theweb embracing the crossbars of the eyes to have force transmittingengagement with the inner surfaces of the crossbars during use of thesling, said crossbars being rigid and undeformable by loads lifted withthe sling, and the inner surfaces of the crossbars being convexly curvedlengthwise thereof so that during use of the sling and application oftension upon the web through an eye, the portion of the web medially ofits side edges is stressed before any load is placed upon the side edgeportions of the web; C. a second rigid crossbar connected to andbridging said other two legs of one of the eyes in parallel spacedrelation to its first mentioned crossbar, the space between the firstand second crossbars and the legs to which they are connected beinglarge enough to permit the eye at the other end of the web to be passedtherethrough to enable the sling to be formed into a loop around a loadto be lifted by a pull on the eye at said other end of the web, and thesurface of the second crossbar which faces the first crossbar beingconvexly curved lengthwise thereof and transversely rounded.